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There's actually a theory that the evolution of humans was affected by what's called the "Saharan Pump", in which the desert/lush cycles of the Sahara trapped and then drove out waves of human evolution into Europe and Asia. One thing people don't realize about the pyramids and other ruins of Ancient Egypt is that at the time they were built the Sahara was in a "lush" cycle. It looked very different then than it does today.

My understanding about the expansion of the universe is that the expansion is only taking place between gravitationally uninvolved objects... in other words, on the scale of galactic clusters. Our bodies are not expanding. The solar system is not expanding. Nor is our galaxy. Nor is our cluster (which I think is called the Virgo supercluster). I used to be under the impression that expansion was happening everywhere, all the time. Then it occurred to me that the speed of light offers a fixed reference frame. If space was expanding everywhere then light would appear to slow down over time.

I've always been a fan of the Big Crunch theory... it satisfies my sense that the state of maximum entropy of the universe is a state of more and more organization. Gas clouds become stars. Stars combine into galaxies. Galaxies combine into super galaxies, on and on until enough matter at sufficient gravity is present to create another in a long line of singularities. "Dark matter" could just be matter that's reached heat death from previous crunches and is therefore undetectable.

The idea of the multiverse and "dark flow" is another fascinating theory. An episode of the always interesting Through the Wormhole dedicated about half an episode to it. The whole episode is worth watching -- it's about most of the things this thread is about -- but the parts dealing with dark flow start about 25 minutes in.

So much of that is so interesting. As far as the Sahara, I didn't know that it likely drove our ancestors into europe. But it makes sense. The documentary I watched did actually mention migration - toward Egypt, because that's where the Nile was, and it became a massive collection of people. And so they suggest that if not for that, Egypt wouldn't have been the great nation-state it was.

The expanding universe thing is something you just educated me on, because like you, I just assumed it was expanding everywhere.

So much of that is so interesting. As far as the Sahara, I didn't know that it likely drove our ancestors into europe. But it makes sense. The documentary I watched did actually mention migration - toward Egypt, because that's where the Nile was, and it became a massive collection of people. And so they suggest that if not for that, Egypt wouldn't have been the great nation-state it was.

Nobody really knows for sure, but they've found cave paintings in areas of Northern Africa that are now desert that depict plants and animals that could only survive in a fertile area. Then when the fossil record shows a more arid climate existed, the cave paintings disappear. Also irrc there used to be a land bridge somewhere in the Mediterranean. I'm assuming it would have connected what is modern day Tunisia through Sicily into Italy (since I think that's the narrowest point of the Mediterranean), but I honestly don't remember.

The expanding universe thing is something you just educated me on, because like you, I just assumed it was expanding everywhere.

Yeah originally it was described to me as like drawing several points on a balloon and then blowing up the balloon. Every point separates from every other point. So I assumed it was happening everywhere but we didn't notice this because the relative size of everything was staying the same. Then two things occurred to me. First, how would that jive with the conservation of mass? Mass can't be added or taken away, so if an object is always expanding, it would be getting progressively less dense. That made me think about orbits... how the orbit of an object around another object is a function of the gravity of the more massive object (it's a function of both, but for the purposes of argument...). My assumption was that an object orbits another object's center of mass (not it's outer layer), which doesn't change if the size of the object changes. In other words, if objects were increasing in size all the time, the orbits of their satellites would not change. They'd remain the same distance from the center of mass of the more massive object until the more massive object increased enough in size that it collided with it's satellite.

I wasn't sure about that, though. How orbits work is nowhere near an area of expertise for me (I wasn't sure how much -- if any -- gravity is a function not just of mass but of density). Then the thing about the speed of light occurred to me. I knew that was a serious flaw in the idea that everything is expanding, so I went and read about it some more and learned what I posted earlier... that objects have to be very far away from each other to experience expansion relative to each other. There are basically these very large blobs of galactic clusters in the universe and it's those clusters that are moving away from each other.

What I want to know is, what is beyond our universe and what exactly is our universe expanding into? Are there other universes in this expanse? Kind of mind-boggling.

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Depends on the theory. Some people believe that the universe has an edge -- hence the title of that Through the Wormhole episode -- and what exists outside it are... other universes? Hamburger stands? Sharks with laser beams attached to their heads?

If the universe is infinite the way I've heard it described is as a kind of mobius loop which folds on itself such that the whole concept of "what's outside" doesn't even make sense. You might be able to go in any direction for a long long time in our universe... an amount of time reaching infinity, and instead of hitting the "wall", you simply find yourself somewhere else in the universe. You don't know how you got there, but there you are. And we aren't able to comprehend it because of our limited ability to make sense of the nature of the universe.

Consider this as a metaphor. Imagine a two dimensional creature. It can only comprehend forward and backward and side to side. It has no idea what up and down are. Say you place this creature on a beach ball. You tell it to drop something to mark it's place and then tell it to walk forward. So the two dimensional creature is walking along and everything's fine. It assumes it's just walking forward in a straight line. That is, until it comes across what it dropped at the beginning of it's journey. How is it possible that it's back where it started? The two dimensional creature cannot comprehend the idea of roundness, so it's totally baffled. Maybe it has some kind of wild eyed theory that works on paper according to it's two dimensional brain, but at a fundamental level every explanation is irrational because the reality is simply beyond it's perception.

If the universe is infinite then it's shape might make perfect sense to a creature that can perceive more dimensions that we can perceive. To us though it's like the beach ball to the two dimensional creature.

My problem with the mobius loop idea is that it counters what we can perceive it terms of very distant objects. Everything we can is see is moving away from us, and at increasing speed the farther we can see. After a certain point galaxies are receding from us at faster than the speed of light (not actually, just relatively), so we can no longer see them (at least I think that's why). The point is at some point if the universe is curved you'd expect to see some distant galaxies coming toward us, but so far as I know none are.

Maybe there's an explanation for that but I just don't know it. Like I said, all of this **** is way over my head.

How orbits work is nowhere near an area of expertise for me (I wasn't sure how much -- if any -- gravity is a function not just of mass but of density).

I realized just how complicated even simple concepts like "mass" are, when I was researching explanations for the higgs boson. There are college websites with forums that argue over even the most elemental concepts. There is much misunderstanding. I came away from it learning a lot but also being confused about a lot.

If the universe is infinite the way I've heard it described is as a kind of mobius loop which folds on itself such that the whole concept of "what's outside" doesn't even make sense. You might be able to go in any direction for a long long time in our universe... an amount of time reaching infinity, and instead of hitting the "wall", you simply find yourself somewhere else in the universe.

I've never learned of the mobius loop before, but you are describing exactly what I've always thought was the nature of the universe. Like dough folding in on itself. There is no outside, and if there was you couldn't ever reach it.

Depends on the theory. Some people believe that the universe has an edge -- hence the title of that Through the Wormhole episode -- and what exists outside it are... other universes? Hamburger stands? Sharks with laser beams attached to their heads?

If the universe is infinite the way I've heard it described is as a kind of mobius loop which folds on itself such that the whole concept of "what's outside" doesn't even make sense. You might be able to go in any direction for a long long time in our universe... an amount of time reaching infinity, and instead of hitting the "wall", you simply find yourself somewhere else in the universe. You don't know how you got there, but there you are. And we aren't able to comprehend it because of our limited ability to make sense of the nature of the universe.

Consider this as a metaphor. Imagine a two dimensional creature. It can only comprehend forward and backward and side to side. It has no idea what up and down are. Say you place this creature on a beach ball. You tell it to drop something to mark it's place and then tell it to walk forward. So the two dimensional creature is walking along and everything's fine. It assumes it's just walking forward in a straight line. That is, until it comes across what it dropped at the beginning of it's journey. How is it possible that it's back where it started? The two dimensional creature cannot comprehend the idea of roundness, so it's totally baffled. Maybe it has some kind of wild eyed theory that works on paper according to it's two dimensional brain, but at a fundamental level every explanation is irrational because the reality is simply beyond it's perception.

If the universe is infinite then it's shape might make perfect sense to a creature that can perceive more dimensions that we can perceive. To us though it's like the beach ball to the two dimensional creature.

My problem with the mobius loop idea is that it counters what we can perceive it terms of very distant objects. Everything we can is see is moving away from us, and at increasing speed the farther we can see. After a certain point galaxies are receding from us at faster than the speed of light (not actually, just relatively), so we can no longer see them (at least I think that's why). The point is at some point if the universe is curved you'd expect to see some distant galaxies coming toward us, but so far as I know none are.

Maybe there's an explanation for that but I just don't know it. Like I said, all of this **** is way over my head.

That makes sense, at least as much as I can understand. It is way over my head as well but is interesting nonetheless.

One thing you mention that has also baffled me is why the expansion is gaining speed? What force us causing it to speed up, shouldn't the laws of nature apply where it maintains inertia until acted upon? Constant speed or even slowing would make more sense than speeding up.

Depends on the theory. Some people believe that the universe has an edge -- hence the title of that Through the Wormhole episode -- and what exists outside it are... other universes? Hamburger stands? Sharks with laser beams attached to their heads?

If the universe is infinite the way I've heard it described is as a kind of mobius loop which folds on itself such that the whole concept of "what's outside" doesn't even make sense. You might be able to go in any direction for a long long time in our universe... an amount of time reaching infinity, and instead of hitting the "wall", you simply find yourself somewhere else in the universe. You don't know how you got there, but there you are. And we aren't able to comprehend it because of our limited ability to make sense of the nature of the universe.

Consider this as a metaphor. Imagine a two dimensional creature. It can only comprehend forward and backward and side to side. It has no idea what up and down are. Say you place this creature on a beach ball. You tell it to drop something to mark it's place and then tell it to walk forward. So the two dimensional creature is walking along and everything's fine. It assumes it's just walking forward in a straight line. That is, until it comes across what it dropped at the beginning of it's journey. How is it possible that it's back where it started? The two dimensional creature cannot comprehend the idea of roundness, so it's totally baffled. Maybe it has some kind of wild eyed theory that works on paper according to it's two dimensional brain, but at a fundamental level every explanation is irrational because the reality is simply beyond it's perception.

If the universe is infinite then it's shape might make perfect sense to a creature that can perceive more dimensions that we can perceive. To us though it's like the beach ball to the two dimensional creature.

My problem with the mobius loop idea is that it counters what we can perceive it terms of very distant objects. Everything we can is see is moving away from us, and at increasing speed the farther we can see. After a certain point galaxies are receding from us at faster than the speed of light (not actually, just relatively), so we can no longer see them (at least I think that's why). The point is at some point if the universe is curved you'd expect to see some distant galaxies coming toward us, but so far as I know none are.

Maybe there's an explanation for that but I just don't know it. Like I said, all of this **** is way over my head.

Exactly right on the 2D creature here is Carl Sagan's take on it: http://www.youtube.com/watch?v=lwL_zi9JNkE
You can argue that a 2D creature cannot fundamentally exist, a creature that was based solely in a 2D world would be as foreign a concept as a creature that was from outside the 4th dimension. We as 3 dimensional creatures are defined by the 4th which is time, time as defined by us a 3 dimensional creature.

I would surmise that a 2D creature would be defined by the 3rd, it would understand the 3rd dimension based upon its definition of that dimension that it gave to it. It would not however understand the 3rd dimension as we understand the dimension since we live in 3 dimensions for a period defined by the 4th dimension.

We would never be able to see a another universe comin' round the mountin', so to speak, because time itself is expending. The time it takes to come around the mountain is equal to the rate of expansion. In 3 dimensions it appears that everything is moving away from everything else but in the 4th dimension (time) everything is standing still relative to each other and time is moving.

Originally Posted by HoneyB

I realized just how complicated even simple concepts like "mass" are, when I was researching explanations for the higgs boson. There are college websites with forums that argue over even the most elemental concepts. There is much misunderstanding. I came away from it learning a lot but also being confused about a lot.

Over time mass will remain constant but the energy state of the mass will change i.e. all compounds will break down into their elemental states and then even further to their sub atomic states and so on. The overall energy of the system remains the same but the size, volume of the system, will increase in time. Gravity is still unexplained on a fundamental level, even if the Higgs Boson is the giver of mass they still have a hard time explaining how it folds into the theory of relativity and quantum mechanics.

This suggests to me that gravity (it is my opinion and nothing more) is a force that is connected to the 4 dimension. Electromagnetic, Strong and Weak Nuclear give you three dimensions, Gravitational gives you the 4th to define the other three. Gravity is time, Gravitational time dilation is real: http://en.wikipedia.org/wiki/Gravita..._time_dilation

It is more than mind boggling to me, I feel like I am missing something grand, I look to the stars and think that is my home, I don't feel the same way about Earth, I feel bound to Earth but that for some reason I should be out there.

Originally Posted by Buddy

That makes sense, at least as much as I can understand. It is way over my head as well but is interesting nonetheless.

One thing you mention that has also baffled me is why the expansion is gaining speed? What force us causing it to speed up, shouldn't the laws of nature apply where it maintains inertia until acted upon? Constant speed or even slowing would make more sense than speeding up.

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If time itself expands and we stand still this would explain this effect. At least in my simple mind it does lol. Someone far smarter might tell me I'm smoking good weed lol